Formation mechanism of aroma compounds in a glutathione-glucose reaction with fat or oxidized fat

Cost-effective production of meaty aroma from porcine cells for hybrid cultivated meat

Cultivated meats are typically hybrids of animal cells and plant proteins, but their high production costs limit their scalability. This study explores a cost-effective alternative by hypothesizing that controlling the Maillard and lipid thermal degradation reactions in pure cells can create a meaty aroma that could be extracted from minimal cell quantities. Using spontaneously immortalized porcine myoblasts and fibroblasts adapted to suspension culture with a 1 % serum concentration, we developed a method to isolate flavor precursors via freeze-thawing. Thermal reaction conditions were optimized to enhance aroma compound production. Chemical profiling demonstrates that myoblasts produce an aroma profile closer to pork meat than fibroblasts, although serum reduction decreased aroma yield. Sensory analysis supported these findings. Incorporating the optimized aroma extract - derived from just 1.2 % (w/w) cells - into plant proteins resulted in a hybrid cultivated meat with 78.5 % sensory similarity to pork meat, but with a significant 80 % reduction in production costs.

Effect of lysine on the cysteine-xylose Maillard reaction to form flavor compounds

To understand flavor formation mechanisms in complex meat-like Maillard systems, effect of lysine on cysteine-xylose reaction to form flavors was studied. GC-MS and GC-O analyses found lysine of 1 times cysteine concentration led to the greatest amount of sulfur-containing meaty compounds while more additional lysine caused more pyrazine compounds. LC-MS analysis showed lysine competed with cysteine to form the early-stage intermediate of Lys-Amadori compounds and accelerated conversion of 2-threityl-thiazolidine-4-carboxylic acids to Cys-Amadori compounds from the cysteine-xylose reaction. Reaction rates based on UV 294 and 420 nm absorbance, browning color, and consumption of cysteine and xylose suggested addition of lysine continuously accelerated the Maillard reaction at intermediate and final stages. Pearson correlation analysis revealed less reaction rates and Lys-Amadori compounds formed could cause more meaty compounds and thereby exposed formation pathways of important aroma compounds. This work can provide guidance for optimizing meat or meat product composition to improve meat flavor.

Effect of frozen storage on the untargeted and targeted metabolites of flavored roasted beef using UHPLC-MS/MS and GC-MS

In this study, we investigated the changes in untargeted metabolites using UHPLC-MS/MS and the flavors of nonflavored (BS1) and flavored (BS2) roasted beef using GC-MS throughout a 6-month frozen period. A total of 509, 659, and 496 metabolites met the conditions for differential screening, and 56, 103, and 47 differential metabolites were recognized between BS1 and BS2 at 0, 3, and 6 months of frozen periods, respectively. The total relative abundance of organic nitrogen compounds, phenylpropanoids, polyketides, organic acids and their derivatives, and benzenoids increased during frozen storage at 3 months and then decreased at 6 months. A total of 16 differential metabolites were identified as markers for prolonged freezing, which belong to organic acids and their derivatives (Asp-Val-Lys, Val-Lys, Met-Phe, Tyr-Leu, N(6)-(octanoyl)lysine, and cis-acetylacrylate), lipids and lipid-like molecules (2,3-dimethyl-3-hydroxyglutaric acid, PC(P-16:0/2:0), (S)-17-hydroxy-9,11,13,15-octadecatetraynoic acid, PC(18:1(9Z)/18:1(11Z)), LysoPC (20:4(8Z,11Z,14Z,17Z)/0:0), PC(20:5/0:0), PE(20:3(8Z,11Z,14Z)/18:4(6Z,9Z,12Z,15Z)), and PS(14:1(9Z)/22:0)), and others (putrescine and phenylacetaldehyde). Sixty-three volatile flavor compounds were detected, and their concentrations were decreased along with frozen storage, except for aldehydes. Positive correlations were observed between volatiles and free amino acids. Therefore, frozen storage has a notable effect on the metabolite profiles of roasted beef.

Impact of Oil Temperature and Splashing Frequency on Chili Oil Flavor: Volatilomics and Lipidomics

In this study, headspace gas chromatography-ion mobility spectrometry, headspace gas chromatography-mass spectrometry, and lipidomics were used to explore the effects of three oil temperatures (210 °C, 180 °C, 150 °C) with single- and traditional triple-oil-splashing processes (210 °C → 180 °C → 150 °C) on the formation of key chili oil aromas. A total of 31 key aroma compounds were identified, with 2,4-nonadienal, α-pinene, α-phellandrene, and β-ocimene being found in all treatment groups. Lipidomics suggested that oleic acid, linoleic acid, and α-linolenic acid were highly positively correlated with key chili oil key aroma compounds, such as (E)-2-heptenal, 2-methylbutyraldehyde, limonene, (E, E)-2,4-heptadienal, 2,4-nonadienal, and 2,4-decadienal. The temperature and frequency of oil splashing significantly affected the chili oil aroma profile (p < 0.05). The citrus, woody, and grassy notes were richer in chili oil prepared at 150 °C, malty and fatty aromas were more prominent at 180 °C, and the nutty aroma was stronger in 210 °C prepared and triple-splashed chili oil. The present study reveals how sequential oil splashing processes synergistically activate distinct lipid degradation pathways compared to single-temperature treatments, providing new insights into lipid-rich condiment preparation, enabling chefs and food manufacturers to target specific aroma profiles.

Insight into the effect of GSH curing treatment on the flavor formation of chicken meat

Glutathione (GSH) is an important precursor of meat flavor. This study aimed to evaluate the effect of GSH-curing on the flavor of cooked chicken. GSH-cured chicken with different concentrations and uncured chicken (blank) were roasted separately and comprehensively analyzed in terms of flavors, odor-active compounds, free amino acids, and fatty acids profile. Volatile flavor compounds were analyzed using solid-phase micro-extraction (SPME) along with GC-MS, GC-O/AEDA, and odor activity value (OAV) calculations. The results showed that the contents of most flavors derived from the Maillard reaction increased due to GSH-curing treatment, such as 2-methylthiophene, 3-methylthiophene, 2-methylthiazole, and 5-methylthiazole, while the lipid degradation flavors reduced, like hexanal, heptanal, and (E,E)-2,4-decadienal. In particular, during sensory analysis, the cured sample with 1.6 mmol GSH had the greatest roasted meaty odor. In addition, GSH curing results in the increased formation of key odor-active substances (OAV ≥ 1), such as 2-acetylthiazole.

Investigation on the pro-aroma generation effects of fatty acids in beef via thermal oxidative models

Fatty acids (FAs) in lipids are important precursors for the formation of meat aroma compounds. However, the specific roles of individual FAs and related reactions in beef aroma formation remain unclear. This study established thermal oxidation models to investigate the impact of different FAs on the formation of beef aroma compounds. The results revealed that thermal oxidation of seven FAs with different saturation produced 42 aroma compounds. Among them, unsaturated fatty acids (UFAs) participating in thermal oxidation degradation is the primary pathway for aroma compound formation, and the types of aroma compounds produced by C18:2n6 and C20:4n6 are similar. The addition of UFAs to lipid-free beef induces lipid oxidation-Maillard reaction interactions, producing more thiophenes, thiazoles, and pyridines, such as 2-acetyl-3-methylthiophene and 2-pentylpyridine, etc. The key aroma compounds in beef with odor characteristics such as fruity, green, fatty or milky are mainly produced by C18:1n9, C18:2n6 and C20:4n6.

Unravelling the formation of characteristic aroma of traditional braised pork through untargeted and targeted flavoromics

Untargeted flavoromics and targeted quantitative analysis of key aroma compounds, and analysis of dynamic change of aroma precursors concentration were used to investigate the aroma evolution of traditional braised pork and the underlying mechanism. The results indicated that lipid oxidation dominated at early cooking stage (0th-45th min), resulting in an increased concentration of most aldehydes, alcohols, ketones, such as hexanal, heptanal, octanal, nonanal, (E)-2-octenal, benzaldehyde, 1-octen-3-ol, and 2,3-octanedione, accompanied with an enhanced unpleasant fatty odor. From 45th to 73rd min, the seasonings alleviated excessive oxidation of unsaturated fatty acids accompanied with decreased aldehydes. Moreover, the diffusion of glucose and amino acids from seasonings to lean meat promoted the consumption of endogenous ribose and amino acids in meat through Maillard reaction, and facilitated the formation of dimethyl trisulfide, dimethyl disulfide, methanethiol, and 2-furfural, which contributed to the meaty, sauce-like, and sweety aroma, thus formed the characteristic aroma of traditional braised pork.

Effects of unsaturated C18 fatty acids on "glucose-glutathione" Maillard reaction: Comparison and formation pathways of initial stage and meaty flavor compounds

To explore the effect of oleic acid, linoleic acid, and linolenic acid on "glucose-glutathione" Maillard reaction initial stage and meaty flavor compounds formation pathways, glutathione-Amadori compound was synthesized, and identified by Q/TOF and NMR. Depending on the concentration of glutathione and glutathione-Amadori compound quantified by UPLC-MS/MS, the unsaturated C18 fat acids inhibited glutathione Amadori compound formation or accelerated degradation, and oleic acid inhibited most markedly. The results showed that 65 volatile compounds were detected by GC-MS-O in four model systems. Particularly, following the addition of unsaturated C18 fatty acids, the content of meaty flavor compounds sequentially decreased from oleic acid to linoleic acid and then to linolenic acid. The CAMOLA (carbohydrate module labeling) demonstrated the 2-methylthiophene, 2-thiophenecarboxaldehyde, 4-mercaptophenol, 2-acetylthiazole, and thieno[3,2-b]thiophene formation pathways. Particularly, we found for the first time that the skeleton of 4-mercaptophenol generated from glucose. The volatile compounds of reaction systems were discriminated by heatmap and PCA analysis. These results highlights the effect of lipid composition on Maillard reaction and contributes to the control of savory flavor.

Exploring the contribution of phosphatidylcholine and triglyceride on the formation of beef aroma-active compounds with thermal oxidation system

Thermal oxidation of phospholipids and triglycerides is a major source of beef aroma compounds. In this study, phosphatidylcholine (PC) and triglyceride (TG) were isolated and purified from beef and added to defatted beef and raw beef. The composition of aroma compounds generated by thermal oxidation in three model systems were compared by flavoromics. The main aroma compounds produced by the thermal oxidation of PC were decanal, (E)-2-nonenal, (E)-2-undecenal, and (E,E)-2,4-decadienal, while the main aroma compounds produced by the thermal oxidation of TG were nonanal, (E)-2-undecenal, and decanal. Nonanal remains the main aroma compound produced by PC and TG in defatted beef. Octanal and nonanal were the major aroma compounds generated by thermal oxidation of raw beef samples spiked with PC and TG. Raw beef with added PC and TG had higher levels of sulfides and heterocycles after thermal oxidation compared to defatted beef with added lipids. The comparison of the aroma profiles in three thermo-oxidative models indicated that PC contributed more than TG to the key odor-active compounds in cooked beef. Additionally, the thermo-oxidative degradation of PC facilitated the formation of Maillard reaction products. However, the beef matrix may inhibit the formation of decanal and (E,E)-2,4-decadienal.

Effect of hot-air drying processing on the volatile organic compounds and maillard precursors of Dictyophora Rubrovalvata based on GC-IMS, HPLC and LC-MS

The dynamic changes in volatile organic compounds (VOCs), reducing sugars, and amino acids of Dictyophora rubrovalvata (DR) at various drying temperatures were analyzed using GC-IMS, HPLC, and LC-MS. Orthogonal partial least squares discriminant analysis (OPLS-DA) combined with VOCs indicated that drying temperature of 80 °C was optimal. Variable importance in the projection (VIP) and relative odor activity value (ROAV) were employed to identify 22 key VOCs. The findings suggested that esters played a predominant role among the VOCs. Pearson correlation analysis revealed that serine (Ser), glutamine (Gln), lysine (Lys), alanine (Ala), threonine (Thr), glutamic acid (Glu), asparagine (Asn), ribose, and glucose were closely associated with the formation of esters, aldehydes, ketones, pyrimidines, and pyrazines. In conclusion, this study laid a foundational theory for elucidating the characteristics aroma substances and their production pathways, providing a valuable reference for analysing the flavor characteristics of DR.

Application of Animal Resources into the Maillard Reaction Model System to Improve Meat Flavor

Simulating meat flavor via Maillard reaction model systems that contain a mixture of amino acids and reducing sugars is an effective approach to understanding the reaction mechanism of the flavor precursors. Notably, animal resources such as fish, beef, chicken, pork hydrolysates, and fats are excellent precursors in promoting favorable meaty and roasted flavors and umami tastes of Maillard reaction products. The experimental conditions and related factors of the model systems for sensory enhancements, debittering, and off-flavor reduction with meat and by-products are summarized in this review. The review also highlights the flavor precursors in the animal resources and their participation in the Maillard reaction. This review provides a basis for a better understanding of the model systems, especially those prepared with animal resources.

Comprehensive foodomics analysis reveals key lipids affect aroma generation in beef

Lipids are vital precursors to beef aroma compounds, but the exact lipid molecules influencing aroma generation remain unconfirmed. This study employs gas chromatography-olfactometry-mass spectrometry and absolute quantitative lipidomics to identify beef's aroma and lipid profiles and to examine lipid alterations post-thermal processing. The aim is to understand the role of lipids in aroma generation during beef's raw-to-cooked transition. Eighteen key aroma compounds were identified as significant contributors to the aroma of beef. 265 lipid molecules were quantified accurately, and we found that triglycerides containing C18:1 or C18:2 chains, such as TG(16:0_18:1_18:1), TG(16:0_18:1_18:2), TG(16:0_16:1_18:1), as well as phosphatidylcholine and phosphatidylethanolamine containing PC(16:1e_20:4), PC(16:0e_20:4), PC(18:2e_18:2), and PE(16:1e_20:4), played important roles in the generation of key aroma compounds in beef. C18:1, C18:2, C18:3, and C20:4 were key substrates for the formation of aroma compounds. In addition, lysophosphatidylcholine and lysophosphatidylethanolamine containing unsaturated fatty acid chains may serve as important aroma retainers.

Characteristic volatile compounds contributed to aroma of braised pork and their precursor sources

The characteristic aroma compounds of traditional braised pork were investigated by gas chromatography-mass spectrometry-olfactometry (GC-MS-O), odor-activity values, and aroma recombination and omission experiments. A total of 56 volatile compounds were detected by GC-MS, among which hexanal, octanal, nonanal, (E)-2-octenal, 2,3-octanedione, 1-octen-3-ol, 2-pentylfuran, methanethiol, and dimethyl trisulfide were identified as the key aroma compounds by molecular sensory science. Partial least squares regression analysis indicated that some aroma compounds significantly contributed to fatty (hexanal, heptanal, 2-pentylfuran, nonanal, and (E)-2-octenal), meaty (methanethiol, dimethyl disulfide, dimethyl trisulfide, and octanal), sauce-like flavor (3-hydroxy-2-butanone and 2-furfural), and sweet, caramel (2,3-octanedione, 1-octen-3-ol). Lean meat produced more aldehydes, alcohols, ketones, and sulfur-containing compounds than subcutaneous fat. The seasonings (saccharose, cooking wine, and soy sauce) facilitated the formation of ethyl L-lactate, 2-acetylfuran, 2-furfural, 5-methyl-2-furaldehyde, 2-methyl-pyrazine, and 2-acetylpyrrole. Meanwhile they reduced the content of lipid oxidation products, thereby stimulated the characteristic aroma of the Chinese traditional braised pork.

Changes in the flavor formation and sensory attributes of Maillard reaction products by different oxidation degrees of beef tallow via cold plasma

It remains unclear how the oxidation degree of animal fat affects the flavor formation and sensory attributes of Maillard reaction products (MRPs). To oxidize beef tallow differentially under mild conditions, an atmospheric pressure cold plasma (APCP) was applied due to its easy, economical, and controllable manipulation and effectiveness. As the duration of APCP increased after 10 min, the oxidation degree of beef tallow increased significantly (p < 0.05). The beef tallow was incorporated into the cysteine-xylose model system and heated at 120 °C for 90 min. Volatiles from lipid oxidation products increased, whereas sulfur-containing compounds decreased significantly when the model included APCP-treated beef tallow (p < 0.05). MRPs with 10-min APCP-treated beef tallow showed reduced off-odor (p < 0.05). Thus, moderate APCP treatment to beef tallow may be beneficial for sensory attributes of MRPs. It suggests the potential of APCP to improve the flavor of heat-sensitive foods by controlling lipid oxidation.

Evaluation of High Vacuum Flavor Extraction Device as a Novel Technique for the Extraction of Volatile Compounds

In this study, a high vacuum flavor extraction (HVE) device was developed to address the limitations of traditional extraction methods, such as extended extraction times and artifact generation during high-temperature processes. Firstly, the repeatability and precision of the HVE method were evaluated through quantitative analysis of twelve volatile odor compounds across seven replicate extractions using gas chromatography-flame ionization detection (GC-FID). The results showed that the HVE system achieved a mean relative standard deviation (RSD) of 11.60 ± 1.79% and a recovery rate of 90.55 ± 4.56%, demonstrating its precision and reproducibility. Secondly, the performance of HVE was compared with solvent-assisted flavor evaporation (SAFE) and simultaneous distillation-extraction (SDE) for extracting flavor compounds from fried tilapia mince. The results indicated that HVE was more effective, particularly in extracting aldehydes and pyrazines, which are key contributors to the flavor profile. Finally, sensory evaluations supported these findings, showing that the odor profiles obtained through HVE were most similar to the original sample, with a similarity score of 72.55%, compared to 69.25% for SAFE and 60.29% for SDE. These findings suggest that HVE is a suitable method for the extraction and analysis of volatile compounds in complex food matrices such as fried tilapia mince.

Characteristics of meat flavoring prepared using hydrolyzed plant protein mix by three different heating processes

Meat flavoring was prepared using mainly enzymatic hydrolysate of plant protein mix, VB1, cysteine, and glucose by three heating processes, including A (80 °C-140 min), B (two-stage, 80 °C-30 min/120 °C-30 min), and C (120 °C-40 min). The A-, B-, and C-heated samples exhibited the strongest fatty and weakest meaty, the strongest meaty and kokumi, and the strongest roasted and bitterness characteristics, respectively. PLS-DA for free amino acids with TAVs and that for SPME/GC-MS results with GC-O and OAVs, suggested three amino acids and eight flavor compounds contributed significantly in differentiating taste or aroma attributes of the three heated samples. Molecular weight distribution and degree of amino substitution suggested 1-5 kDa peptides contributed to kokumi taste. Overall, C- and A-heating exhibited the highest rates in Maillard reaction and lipid oxidation, respectively, while those of B heating were between these two heating processes and responsible for better flavor of meat flavoring.

The Maillard reactions: Pathways, consequences, and control

The century old Maillard reactions continue to draw the interest of researchers in the fields of Food Science and Technology, and Health and Medical Sciences. This chapter seeks to simplify and update this highly complicated, multifaceted topic. The simple nucleophilic attack of an amine onto a carbonyl group gives rise to a series of parallel and subsequent reactions, occurring simultaneously, resulting into a vast array of low and high mass compounds. Recent research has focused on: (1) the formation and transformation of α-dicarbonyl compounds, highly reactive intermediates which are essential in the development of the desired color and flavor of foods, but also lead to the production of the detrimental advanced glycation end products (AGEs); (2) elucidation of the structures of melanoidins in different foods and their beneficial effects on human health; and (3) harmful effects of AGEs on human health. Considering that MRs have both positive and negative consequences, their control to accentuate the former and to mitigate the latter, is also being conscientiously investigated with the use of modern techniques and technology.

Unraveling the flavor profiles of chicken meat: Classes, biosynthesis, influencing factors in flavor development, and sensory evaluation

Chicken is renowned as the most affordable meat option, prized by consumers worldwide for its unique flavor, and universally recognized for its essential savory flavor. Current research endeavors are increasingly dedicated to exploring the flavor profile of chicken meat. However, there is a noticeable gap in comprehensive reviews dedicated specifically to the flavor quality of chicken meat, although existing reviews cover meat flavor profiles of various animal species. This review aims to fill this gap by synthesizing knowledge from published literature to describe the compounds, chemistry reaction, influencing factors, and sensory evaluation associated with chicken meat flavor. The flavor compounds in chicken meat mainly included water-soluble low-molecular-weight substances and lipids, as well as volatile compounds such as aldehydes, ketones, alcohols, acids, esters, hydrocarbons, furans, nitrogen, and sulfur-containing compounds. The significant synthesis pathways of flavor components were Maillard reaction, Strecker degradation, lipid oxidation, lipid-Maillard interaction, and thiamine degradation. Preslaughter factors, including age, breed/strain, rearing management, muscle type, and sex of chicken, as well as postmortem conditions such as aging, cooking conditions, and low-temperature storage, were closely linked to flavor development and accounted for the significant differences observed in flavor components. Moreover, the sensory methods used to evaluate the chicken meat flavor were elaborated. This review contributes to a more comprehensive understanding of the flavor profile of chicken meat. It can serve as a guide for enhancing chicken meat flavor quality and provide a foundation for developing customized chicken products.

Thiamine, cysteine and xylose added to the Maillard reaction of goat protein hydrolysate potentiates the formation of meat flavoring compounds

A protein hydrolysate of goat viscera added with xylose, cysteine, and thiamine under different pH was used to prepare a meat flavoring. Goat viscera hydrolysate and flavoring were subjected to analysis of physicochemical characteristics, amino acid profile, sugars, fatty acids, and volatile profile. Meat aroma characteristics were initiated in the hydrolysate, in which Strecker's pyrazines and aldehydes were identified, which also had fatty acids and amino acids available for the formation of 96 volatile compounds in the flavorings via lipid manipulation, Maillard occurrence, Strecker manipulation and interactions among these means. Maillard reaction products with intense meat aroma, such as 2-methyl-3-furanthiol, 2-furfurylthiol and, bis(2-methyl-3-furyl) disulfide were isolated only in the flavoring at pH 4. In contrast, the flavoring at pH 6 showed a higher concentration than all the other compounds, providing a lower meat characteristic, but an intense sweet, fatty and goat aroma.

The interaction between lipid oxidation and the Maillard reaction model of lysine-glucose on aroma formation in fragrant sesame oil

The formation mechanism behind the sophisticated aromas of sesame oil (SO) has not been elucidated. The interaction effects of the Maillard reaction (MR) and lipid oxidation on the aroma formation of fragrant sesame oil were investigated in model reaction systems made of l-lysine (Lys) and d-glucose (Glc) with or without fresh SO (FSO) or oxidized SO (OSO). The addition of OSO to the Lys-Glc model increased the MR browning at 294 nm and 420 nm and enhanced the DPPH radical scavenging activity greater than the addition of FSO (p < 0.05). The presence of lysine and glucose inhibited the oxidation of sesame oil, reduced the loss of γ-tocopherol, and facilitated the formation of sesamol (p < 0.05). The Maillard-lipid interaction led to the increased concentrations of some of the alkylpyrazines, alkylfurans, and MR-derived ketones and acids (p < 0.05) while reducing the concentrations of other pyrazines, lipid-derived furans, aliphatic aldehydes, ketones, alcohols, and acids (p < 0.05). The addition of FSO to the MR model enhanced the characteristic roasted, nutty, sweet, and fatty aromas in sesame oil (p < 0.05), while excessive lipid oxidation (OSO) brought about an unpleasant oxidized odor and reduced the characteristic aromas. This study helps to understand the sophisticated aroma formation mechanism in sesame oil and provides scientific instruction for precise flavor control in the production of sesame oil.

The number and position of unsaturated bonds in aliphatic aldehydes affect meat flavorings system: Insights on initial Maillard reaction stage and meat flavor formation from thiazolidine derivatives

Nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal, and (E,Z)-2,6-nonadienal were used to study the effect of number and position of the unsaturated bond in aliphatic aldehydes on meat flavorings. Cysteine-Amadori and thiazolidine derivatives were synthesized, identified by UPLC-TOF/MS and NMR, and quantitatively by UPLC-MS/MS. The polyunsaturated aldehydes exhibited higher inhibition than monounsaturated aldehydes, and monounsaturated aldehydes exhibited higher inhibition than saturated aldehydes, mainly manifested by the inhibition of the cysteine-Amadori formation and acceleration of the thiazolidine derivatives formation. The effect of unsaturated bonds position in aliphatic aldehydes on the initial Maillard reaction stage was similar. The cysteine played an important role in catalyzing the reaction of aliphatic aldehydes. A total of 109 volatile compounds derived by heating prepared thiazolidine derivatives degradation were detected by GC-MS. Formation pathways of volatile compounds were proposed by retro-aldol, oxidation, etc. Particularly, a route to form thiazole by the decarboxylation reaction of thiazolidine derivatives which derivatives from formaldehyde reacting with cysteine was proposed.

Comparison of the Fatty Acid Composition and Small Molecular Metabolites between Yanjin Blackbone Chicken and Piao Chicken Meat

The fatty acid composition and small molecular metabolites in breast and leg meat of Yanjin blackbone chickens (YBC) and Piao chickens (PC) were detected by gas chromatography-mass spectrometry and liquid chromatography-quadrupole static field orbital trap mass spectrometry. Thirty-two fatty acids were detected, and the total fatty acid content of PC was significantly higher than that of YBC (p<0.05). Oleic acid, linoleic acid, palmitic acid, stearic acid, and arachidonic acid were the main fatty acids in the two chicken varieties, and the composition of fatty acids in the two varieties were mainly unsaturated fatty acids, being more than 61.10% of the total fatty acids. Meanwhile, 12 and 16 compounds were screened out from chicken legs and chicken breasts of YBC and PC, respectively, which had important contributions to the differences between groups.

The number and position of unsaturated bonds in aliphatic aldehydes affect the cysteine-glucose Maillard reaction: Formation mechanism and comparison of volatile compounds

Nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal, and (E,Z)-2,6-nonadienal were used to reveal the effect of the number and position of unsaturated bond in aliphatic aldehydes on Maillard reaction for the generation of 88 stewed meat-like volatile compounds. The results showed that (E,E)-2,4-nonadienal and (E,Z)-2,6-nonadienal exhibited greater inhibition of the cysteine reaction with glucose than nonanal and (E)-2-nonenal. However, the positions of the unsaturated bonds in aliphatic aldehydes in the Maillard reaction stage were similar. A carbohydrate module labeling approach was used to present the formation pathways of 34 volatile compounds derived from the Maillard reaction with aliphatic aldehyde systems. The number and position of unsaturated bonds in aliphatic aldehydes generate multiple pathways of flavor compound formation. 2-Propylfuran and (E)-2-(2-pentenyl)furan resulted from aliphatic aldehydes. 5-Butyldihydro-2(3H)-furanone and 2-methylthiophene were produced from the Maillard reaction. 2-Furanmethanol, 2-thiophenecarboxaldehyde, and 5-methyl-2-thiophenecarboxaldehyde were derived from the interaction of aliphatic aldehydes and the Maillard reaction. In Particular, the addition of aliphatic aldehydes changed the formation pathway of 2-propylthiophene, thieno[3,2-b]thiophene, and 2,5-thiophenedicarboxaldehyde. Heatmap and PLS-DA analysis could discriminate volatile compound compositions of the five systems and screen the marker compounds differentiating volatile compounds.

Aging mechanism for improving the tenderness and taste characteristics of meat

Tenderness and taste characteristics of meat are the key determinants of the meat choices of consumers. This review summarizes the contemporary research on the molecular mechanisms by which postmortem aging of meat improves the tenderness and taste characteristics. The fundamental mechanism by which postmortem aging improves the tenderness of meat involves the operation of the calpain system due to apoptosis, resulting in proteolytic enzyme-induced degradation of cytoskeletal myofibrillar proteins. The improvement of taste characteristics by postmortem aging is mainly explained by the increase in the content of taste-related peptides, free amino acids, and nucleotides produced by increased hydrolysis activity. This review improves our understanding of the published research on tenderness and taste characteristics of meat and provides insights to improve these attributes of meat through postmortem aging.

Dynamic changes in the water distribution and key aroma compounds of roasted chicken during roasting

The effects of roasting times (0, 2, 4, 6, 8, 10, 12, and 14 min) on the dynamic changes of the water distribution and key aroma compounds in roasted chicken during the electric roasting process were studied. In total, 36 volatile compounds were further determined by GC-MS and 11 compounds, including 1-octen-3-ol, 1-heptanol, hexanal, decanal, (E)-2-octenal, acetic acid hexyl ester, nonanal, 2-pentylfuran, heptanal, (E, E)-2,4-decadienal and octanal, were confirmed as key aroma compounds. The relaxation time of T22 and T23 was increased first and then decreased, while the M22 and M23 in roasted chicken were decreased and increased with increasing roasting time, respectively. The fluidity of the water in the chicken during the roasting process was decreased, and the water with a high degree of freedom migrated to the water with a low degree of freedom. In addition, the L*, a*, b*, M23 and all amino acids were positively correlated with all the key aroma compounds, while T22, M22 and moisture content were negatively correlated with all the key aroma compounds.

Lipid oxidation and flavor changes in saturated and unsaturated fat fractions from chicken fat during a thermal process

Chicken fat, due to its rich fatty acids (FAs), is more prone to lipid oxidation and the production of volatile compounds. The aim of the present study was to investigate the oxidative characteristics and flavor changes of saturated (SFF) and unsaturated fat fractions (USFF) from chicken fat induced by heating (140 °C at 70 rpm min-1 for 1 h and 2 h: SFF1, USFF1, SFF2 and USFF2). The FAs and volatile compounds were analyzed by gas chromatography-mass spectrometry (GC-MS) and two-dimensional gas chromatography time of flight mass spectrometry (GC × GC-ToFMS), respectively. The results showed that higher contents of unsaturated fatty acids (UFAs) were found in USFF compared to that in SFF, whereas USFF showed lower levels of saturated fatty acids (SFAs). With the extension of heating time, the SFA/UFA ratio in USFF and SFF significantly increased (p < 0.05), and more aldehydes, alcohols, ketones, and lactones were formed. Moreover, the odor activity values of 23 important compounds in USFF1-2 were significantly higher (p < 0.05) than those in SFF1-2. As revealed by principal component analysis (PCA) and cluster analysis (CA), it was obviously observed that all samples were divided into four clusters (USFF-SFF, USFF1-SFF1, USFF2, and SFF2). According to correlation analysis between FAs and volatile compounds, C18:2 ω6, C18:3 ω6 and C18:3 ω3 were significantly associated with dodecanal, (Z)-3-hexenal, (E)-2-decenal, 2-undecenal, (E)-2-dodecenal, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, 2-decanone, γ-octalactone and γ-nonalactone. Our data elucidated that fat fractions from chicken fat with varying degrees of saturation could impart different flavor characteristics during a thermal process.

Roles of sulfur-containing compounds in fermented beverages with 2-furfurylthiol as a case example

Aroma is a critical component of the flavor and quality of beverages. Among the volatile chemicals responsible for fragrance perception, sulfur compounds are unique odorants due to their extremely low odor threshold. Although trace amounts of sulfur compounds can enhance the flavor profile of beverages, they can lead to off-odors. Sulfur compounds can be formed via Maillard reaction and microbial metabolism, imparting coffee aroma and altering the flavor of beverages. In order to increase the understanding of sulfur compounds in the field of food flavor, 2-furfurylthiol (FFT) was chosen as a representative to discuss the current status of their generation, sensory impact, enrichment, analytical methods, formation mechanisms, aroma deterioration, and aroma regulation. FFT is comprehensively reviewed, and the main beverages of interest are typically baijiu, beer, wine, and coffee. Challenges and recommendations for FFT are also discussed, including analytical methods and mechanisms of formation, interactions between FFT and other compounds, and the development of specific materials to extend the duration of aroma after release.

Formation, migration, derivation, and generation mechanism of polycyclic aromatic hydrocarbons during frying

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and lipophilic, which can be found in frying system. This review summarized the formation, migration and derivation for PAHs, hypothesized the possible mechanism for PAHs generation during frying and presented the research prospects. Some factors like high oil consumption, high temperature, long time and oil rich in unsaturated fatty acids promoted the formation of PAHs and the presence of antioxidants inhibited the PAHs formation. The effect of proteins and carbohydrates in foods on the formation of PAHs is inconclusive. The formed PAHs were migrated into food and air. Moreover, some PAHs transformed into more toxic PAHs-derivatives during frying. The generation of PAHs may be related to low-barrier free radical-mediated reaction and the unsaturated hydrocarbons may be precursors of PAHs during frying. In future, the isotope tracer technology and on-line detection may be applied to discover intermediates and provide clues for studying PAHs generation mechanisms.

Sensory attributes and functional properties of maillard reaction products derived from the crassosotrea gigas (Ostrea rivularis gould) enzymatic hydrolysate and xylose system

To improve the flavor of Ostrea rivularis Gould, enzymatic hydrolysis was conducted and xylose-OEH Maillard reaction products were prepared. Then, their physicochemical properties and metabolites were determined by UHPLC-MS-MS, and volatile compounds were determined by GC-MS to investigate the changes. The results showed that His, Gln, Lys, Asp, and Cys were the major amino acids consumed. After being heated at 120 °C for up to 150 min, the DPPH (2,2-Diphenyl-1-picrylhydrazyl) was 85.32 ± 1.35% and the reducing capacity was 1.28 ± 0.12. Both were the highest in the groups. Additionally, 45 volatile compounds, including 2-ethyl-5-methyl-pyrazine and 2-ethyl-3,5-dimethyl-pyrazine, and 678 compounds were identified. We also found that 18 metabolites with significant differences (VIP ≥2) were differential metabolites, which involved lipid oxides and amino acid derivatives. The content of lipids favored the regulation of Maillard products and affected the lower threshold of the flavor of aldehydes, which contributed to the flavor and antioxidant activity. These results suggested the potential of xylose-OEH MRPs as a natural antioxidant for further processing oysters.

GC-MS and GC×GC-ToF-MS analysis of roasted / broth flavors produced by Maillard reaction system of cysteine-xylose-glutamate

Maillard reaction products (MRPs) with roasted/broth flavors were prepared and analyzed for the resulting flavor differences. The identification of volatile compounds in MRPs was carried out by GC-MS and GC × GC-ToF-MS. A total of 88 compounds were identified by GC-MS; 130 compounds were identified by GC × GC-ToF-MS, especially acids and ketones were identified. Principal component analysis (PCA) was used to visualize the volatile compounds, and the roasted/broth flavors were differentiated. The contents and types of pyrazines were more in roasted flavors; thiol sulfides and thiophenes were more in broth flavors. All in all, the differences in volatile compounds producing roasted/broth flavors were studied through the cysteine-xylose-glutamate Maillard reaction system, which provided a theoretical basis for the future use of Maillard reaction to simulate meat flavor.

Effect of Aliphatic Aldehydes on Flavor Formation in Glutathione-Ribose Maillard Reactions

The Maillard reaction (MR) is affected by lipid oxidation, the intermediate products of which are key to understanding this process. Herein, nine aliphatic aldehyde−glutathione−ribose models were designed to explore the influence of lipid oxidation products with different structures on the MR. The browning degree, fluorescence degree, and antioxidant activity of the MR products were determined, and the generated volatile organic compounds (VOCs) and nonvolatile compounds were analyzed by gas chromatography-mass spectrometry and ultra-performance liquid chromatography-mass spectrometry. A total of 108 VOCs and 596 nonvolatile compounds were detected. The principal component and hierarchical clustering analyses showed that saturated aldehydes mainly affected the VOCs generated by the MR, while unsaturated aldehydes significantly affected the nonvolatile compounds, which changed the taste attributes of the MR products. Compared with the control group, the addition of unsaturated aldehydes significantly increased the sourness score and decreased the umami score. In addition, the addition of unsaturated aldehydes decreased the antioxidant activity and changed the composition of nonvolatile compounds, especially aryl thioethers and medium chain fatty acids, with a strong correlation with umami and sourness in the electronic tongue analysis (p < 0.05). The addition of aliphatic aldehydes reduces the ultraviolet absorption of the intermediate products of MR browning, whereas saturated aldehydes reduce the browning degree of the MR products. Therefore, the flavor components of processed foods based on the MR can be effectively modified by the addition of lipid oxidation products.

Effects of supplemental different clay minerals in broiler chickens under cyclic heat stress

The objective of this study was to investigate the effect of supplementing clay minerals and organic chromium in feed on broiler chicken under heat stress (HS). A total of 90 one-day-old broiler chicken (Arbor Acres) with an initial body weight of 45.0 ± 0.2 g were assigned to five treatment groups (six replications, three birds each cage): 1) NC group, basal diet under room temperature environment; 2) PC group, basal diet under high temperature (HT) environment; 3) ILT group, basal diet + 1% illite + HT; 4) ZLT group, basal diet + 1% zeolite + HT; 5) OC group, basal diet + 400 ppb/kg organic chromium + HT. The ILT and ZLT groups had significantly higher body weight than the PC group in 4 weeks. Apparent total tract digestibility of gross energy was increased in the ILT, ZLT, and OC groups compared to the PC group. The NC group had lower foot-pad dermatitis score than other groups. Escherichia coli population in the cecum and feces was decreased in the ZLT group than in the PC group. Lactobacillus in cecum and feces was significantly increased in the ZLT group than in the PC group. Regarding blood profiles, blood cortisol was decreased in the NC and ILT groups compared to the PC group. Water holding capacity and pH were increased in the ZLT group than the PC group. In conclusion, according to the results of growth performance, nutrients digestibility, bacteria counts, and meat characteristics, supplementation of the ZLT in broiler diet can alleviate HS.

Flavor formation based on lipid in meat and meat products: A review

Meat product is popular throughout the world due to its unique taste. Flavor is one of the most important quality characteristics of meat products and also is a key influencing factor in the overall acceptability of meat products. The flavor of meat products is formed by precursors undergoing a series of complex reactions. During meat product processing, lipids are hydrolyzed by lipase to produce flavor precursors such as free fatty acid, then further oxidized to form volatile flavor compounds. This review summarizes lipolysis, lipid oxidation, and interaction of lipid with Maillard reaction and amino acid during meat products processing and storage as well as influencing factors on lipid degradation including raw meat (source of meat, feeding pattern, and castration), processing methods (thermal processing, nonthermal processing, salting, and fermentation) and additives. Meanwhile, the volatile compounds produced by lipids in meat products including aldehydes, alcohols, ketones, and hydrocarbons are summed up. Analytical methods of volatile compounds and the application of lipidomics analysis in mechanisms of flavor formation of meat products are also reviewed. PRACTICAL APPLICATIONS: Flavor is one of the most important quality characteristics of meat products, which influences the acceptability of meat products for consumption. Lipids play an important role in the flavor formation of meat products. Understanding the relationship between flavor compounds and changes in lipid compositions during the processing and storage of meat products will be helpful to control the quality of meat products.

Ultrasound-Assisted Preparation of Maillard Reaction Products Derived from Hydrolyzed Soybean Meal with Meaty Flavor in an Oil-In-Water System

In the present work, we prepared Maillard reaction products (MRPs) derived from enzyme hydrolyzed soybean meal with ultrasound assistance in an oil-(oxidized lard)-in-water system (UEL-MRPs) or oil-free system (UN-MRPs), and the effect of ultrasound on the properties of the obtained MRPs was evaluated. The analysis of fatty acids in lard with different treatments showed that ultrasound can generate more unsaturated fatty acids in the aqueous phase. The UV–Vis absorbances of UEL-MRPs, UN-MRPs, and MRPs obtained in an oil-in-water system (EL-MRPs) and MRPs obtained in an oil-free system (N-MRPs) at 294 and 420 nm indicated that ultrasound could increase the amount of Maillard reaction intermediates and melanoids in the final products of the Maillard reaction. This was in line with the result obtained from color change determination—that ultrasound can darken the resultant MRPs. Volatile analysis showed ultrasound can not only increase the number of volatile substances, but also greatly increase the composition of volatile substances in UEL-MRPs and UN-MRPs, especially the composition of those contributing to the flavor of the MRPs, such as oxygen-containing heterocycles, sulfur-containing compounds, and nitrogen-containing heterocycles. Descriptive sensory evaluation revealed that UN-MRPs and UEL-MRPs had the highest scores in total acceptance, ranking in the top two, and UEL-MRPs had the strongest meaty flavor among these four kinds of MRPs. Furthermore, the measurements of antioxidant activities, including DPPH radical-scavenging activity, hydroxyl radical scavenging ability, and ferric ion reducing antioxidant power, were conducted, showing that UN-MRPs exhibited the highest antioxidant activity among all the MRPs.

Producing beef flavors in hydrolyzed soybean meal-based Maillard reaction products participated with beef tallow hydrolysates

This work investigated the effect of oxidized beef tallow on the volatile compositions and sensory properties of soybean meal-based Maillard reaction products (MRPs). Various tallow oxidation methods included thermal treatment (TT), enzymatic hydrolysis (ET) and enzymatic hydrolysis combined with mild thermal (ETT) treatment. Results showed that all these oxidized tallow contained more types of volatile compounds than those of untreated tallow. Moreover, the composition of almost all types of volatile substances was greatly increased with the addition of the oxidized beef tallow into the hydrolyzed soybean meal-based Maillard reaction system. More importantly, the composition of oxygen-containing heterocycles (63.89 μg/mL), sulfur-containing compounds (76.64 μg/mL), and nitrogen-containing heterocycles (19.81 μg/mL) that contribute positively to sensory properties in ETT-MRPs was found to be the highest among all the MRPs. Correlation assessment revealed that ETT was closely related to the most typical volatile products and sensory attributes, indicating this approach can effectively enhance the sensory and flavor of hydrolyzed soybean meal derived MRPs.

Analysis of key precursor peptides and flavor components of flaxseed derived Maillard reaction products based on iBAQ mass spectrometry and molecular sensory science

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Peptides-MRPs had high umami, mouthfulness, and continuity enhancement.

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DLSFIP and ELPGSP accounted for 42.22% and 20.41% of total consumption.

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Sulfur and nitrogen flavors was dependent on cysteine and peptides, respectively.

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This study also revealed the flavor formation mechanism of flaxseed derived MRPs.

Flaxseed derived Maillard reaction products (MRPs) have typical meaty flavor, but there is no report on comparison of their amino acids and peptides reactivity. The peptides and amino acids of flaxseed protein hydrolysates were separately collected by G-15 gel chromatography. Taste dilution analysis (TDA) showed that peptides-MRPs had high umami, mouthfulness, and continuity enhancement. Further, LC-MS/MS revealed that flaxseed protein hydrolysates consumed 41 peptides after Maillard reaction. Particularly, DLSFIP (Asp-Leu-Ser-Phe-Ile-Pro) and ELPGSP (Glu-Leu-Pro-Gly-Ser-Pro) accounted for 42.22% and 20.41% of total consumption, respectively. Aroma extract dilution analysis (AEDA) indicated that formation of sulfur-containing flavors was dependent on cysteine, while peptides were more reactive than amino acids for nitrogen-containing heterocycles. On the other hand, 11 flavor compounds with flavor dilution (FD) ≥ 64 were identified for flaxseed derived MRPs, such as 2-methylthiophene, 2-methyl-3-furanthiol, furfural, 2-furfurylthiol, 3-thiophenethiol, thieno[3,2-b] thiophene, 2,5-thiophenedicarboxaldehyde, 2-methylthieno[2,3-b] thiophene, 1-(2-methyl-3-furylthio)-ethanethiol, 2-methylthieno[3,2-b] thiophene, and bis(2-methyl-3-furyl)-disulfide. In addition, we further demonstrated the flavors formation mechanism of flaxseed derived MRPs.

Characterization of Thermally Induced Flavor Compounds from the Glucosinolate Progoitrin in Different Matrices via GC-TOF-MS

As important flavor precursors, glucosinolates are ubiquitous in the plant family of Brassicaceae. Glucosinolate degradation products are the major volatile flavor compounds of rapeseed oil, accounting for up to 80% of the total volatiles. However, up to now, little attention has been paid to the volatile flavor products of the nonenzymatic thermal degradation of glucosinolates. One of the most important factors that determine the flavor of hot-pressed rapeseed oil is the roasting process, where the thermal degradation of glucosinolates mainly occurs. The thermal degradation behavior and volatile products of progoitrin (the main glucosinolate of rapeseed) in different matrices (phosphate buffer at a pH value of 5.0, 7.0, or 9.0, sea sand, and rapeseed powder) at different temperatures (150-200 °C) and times (0-60 min) were studied using HPLC and GC-TOF-MS. Thereby, the degradation rate of progoitrin decreased in the following order: pH 9.0 > sea sand > rapeseed powder > pH 7.0 > pH 5.0. Further, a higher degradation was observed with increasing temperature and time. Under the applied conditions in this study, 2,4-pentadienenitrile was the major nitrile and thiophenes were the major sulfur-containing volatile compounds formed. Possible formation pathways of main sulfur-containing and nitrogen-containing volatiles were proposed.

Maillard reaction of food-derived peptides as a potential route to generate meat flavor compounds: A review

Plant-based meat analogues (PBMA) are promising foods to address the global imbalance between the supply and demand for meat products caused by the increasing environmental pressures and growing human population. Given that the flavor of PBMA plays a crucial role in consumer acceptance, imparting meat-like flavor is of great significance. As a natural approach to generate meat-like flavor, the Maillard reaction involving food-derived peptides could contribute to the required flavor compounds, which has promising applications in PBMA formulations. In this review, the precursors of meat-like flavor are summarized followed by a discussion of the reactions and mechanisms responsible for generation of the flavor compounds. The preparation and analysis techniques for food-derived Maillard reacted peptides (MRPs) as well as their taste and aroma properties are discussed. In addition, the MRPs as meat flavor precursors and their potential application in the formulation of PBMA are also discussed. The present review provides a fundamental scientific information useful for the production and application of MRPs as meat flavor precursors in PBMA.

Carcass Traits, Meat Quality, and Volatile Compounds of Lamb Meat from Different Restricted Grazing Time and Indoor Supplementary Feeding Systems

This study was conducted to investigate the carcass traits, meat quality, and volatile compounds of growing lambs under different restricted grazing time and indoor supplementary feeding systems. Fifty 3-month-old male Tan lambs (with similar body weight) were divided into five groups randomly according to grazing time 12 h/d (G12), 8 h/d(G8), 4 h/d(G4), 2 h/d (G2), and 0 h (G0, indoor supplementary feeding). Animals were slaughtered at the end of the experiment, and the longissimus thoracis (LT) samples were collected for further analysis. The results indicated that indoor supplementary feeding improved the percentages of carcass fat and non-carcass fat of pre-slaughter weight (PSW) and decreased the cooking loss of lamb meat. Grazing for 8 h/d or 2 h/d enhanced PSW, carcass, and meat percentages of PSW. Lambs grazing for 2 h/d with supplement and indoor supplementary feeding lambs had a higher level of intramuscular fat and lightness (L*) value and lower cooking loss in the LT muscle, but higher yellowness (b*) and fat content were found in indoor supplementary feeding lambs. More categories of volatile compounds were identified in meat from grazing lambs than from indoor supplementary feeding lambs, but lower content of aldehydes and total volatile flavor compounds was detected in grazing lambs. Overall, the results demonstrated that the feeding system is a main factor that affects lamb meat quality, and proper grazing time can improve the quantity and quality of lamb meat and provide meat with different flavors to the consumers.

Supplementation of Mixed Organic Acids Improves Growth Performance, Meat Quality, Gut Morphology and Volatile Fatty Acids of Broiler Chicken

Simple Summary

Organic acid as a green feed additive is increasingly favoured by enterprises and scholars, but little emphasis has been placed on the effect of organic acids on broiler meat quality and lipid profile. Therefore, this study observed that mixed organic acids improve broiler growth performance, meat quality as well as muscle lipid profile, which suggests that mixed organic acids can be an effective measure to prevent meat quality decline in chicken meat.

Abstract

Background: Organic acid as a green feed additive is increasingly favoured by enterprises and scholars, but little emphasis has been placed on the effect of organic acids on broiler meat quality. Methods: A total of 192 male chicks (one-day-old, weighted 48.40 ± 0.64 g) were selected to investigate the effect of mixed organic acids (MOA) on growth performance, meat quality as well as fatty acids profile. Chicks were randomly allocated to three treatments with eight replicates and eight chicks per replicate, including a corn–soybean basal diet with 0 (CON), 3000 mg/kg (low MOA; LMOA), and 6000 mg/kg (high MOA; HMOA) MOA. The experiment was divided into starter (d 1–d 21) and grower (d 22–d 42) phases. Results: Broilers supplemented with LMOA and HMOA enhanced (p < 0.05) the final body weight and average daily gain in the grower and overall phases. An improved (p < 0.05) feed conversion ratio in the grower and overall phases was observed in broilers supplemented with LMOA. The breast and thigh muscles pH24h were higher (p < 0.05) in broilers fed with HMOA and the redness in thigh meat was also improved (p < 0.05). Additionally, supplementing LMOA increased (p < 0.05) the saturated fatty acids, unsaturated fatty acids and the ratio of polyunsaturated fatty acids to saturated fatty acids in breast meat. A positive effect occurred (p < 0.05) on jejunal villus height and ileal crypt depth in 21 d broilers supplemented with HMOA. Conclusion: Our findings indicated that dietary supplementation of MOA could improve the growth performance, meat quality, and fatty acids profile, as well as intestinal morphology. Furthermore, diets supplemented with mixed organic acids at 3000 mg/kg may be more desirable, considering the overall experimental results in broilers.

The effect of aging on beef taste, aroma and texture, and the role of microorganisms: a review

The present review summarizes the advantages and disadvantages of three different aging methods (traditional dry aging, wet aging in vacuum shrink pack and dry aging in a highly moisture-permeable bag), discusses the effects of aging on beef which focus on the formation of taste-active compounds and aroma-active compounds and texture changes, and speculates the role of microbes. All these three aging methods can improve the aroma, flavor and texture of beef to varying degrees. It is concluded that the improvement in the taste during aging may be attributed to the following three aspects: First, the release of reducing sugars from the transition of glycogen and ATP; Second, the formation of free amino acids (FAAs) and peptides through proteolysis; Third, IMP, GMP, inosine and hypoxanthine which are produced by the degradation of nucleotides. The improvement of aroma is related to the volatile aroma-active components, which are produced by the thermal oxidation/degradation of fatty acids and the Maillard reaction between amino acids and reducing sugars during aging. And the change of texture is mainly owing to the degradation of cytoskeletal myofibrin and collagen with intramural connective tissue in meat by the endogenous proteolysis system. The role of microorganism in aging will be the main direction of further research.